Repeat keratoplasty for correction of high or irregular postkeratoplasty astigmatism in clear corneal grafts

R. Collagen imaging reveals synergistic effects of sutures and host-donor misalignment on topographical irregularities in penetrating keratoplasty

PURPOSE

Mitigating unwanted refractive errors is crucial for surgeons to ensure quality vision after penetrating keratoplasty (PK). The primary objective of the present study is to highlight the importance of microstructural matching of the host and the donor cornea during PK on the distribution of the corneal tissue while suturing.

METHODS

For this purpose, the present study undertakes an in-vitro PK model to analyse the effect of suturing and host-donor misalignment on corneal birefringence. Five groups of experiments were performed using five corneoscleral buttons. In each group, N = 16 data points (corresponding to 16 simple interrupted sutures) were assessed before and after PK with five degrees of misalignments, 0°, 30°, 45°, 60° and 90° to detect the variations in corneal birefringence post-PK. The technique of digital photoelasticity is utilized to capture the corneal birefringence experimentally.

RESULTS

The local and global features of corneal birefringence provided interesting insights into the nuances of corneal birefringence in PK. Statistical analysis was performed to study the effects of suturing on the birefringence around the suture bites. It was observed that the interaction of the suture tension and structural misalignment between the host and the donor cornea influences the corneal birefringence in PK. Conclusions The zero-degree structural misalignment of the host and the donor tissue is preferable to minimize the topographical irregularities and related astigmatism post-PK. The findings of the present study envisage an additional step of structurally aligning the donor tissue with the host before suturing to minimize topographical irregularities in PK.

Managing Post Keratoplasty Astigmatism

Corneal transplantation, when used in the correct setting, can significantly improve visual acuity and therefore quality of life. One of the barriers to good vision following keratoplasty is residual post operative surgical astigmatism. Following a thorough literature search, we present the different options available to readers, with regards to how post-operative astigmatism can be approached and managed in order to improve vision. We present available data from the literature, which in some areas are scarce, with a view to collating all of this information in one place, allowing comparison between different modalities of treatment.

Safety and efficacy of a laser refractive procedure in eyes with previous keratoplasty: systematic review and meta-analysis

Post-keratoplasty (KP) patients' visual acuity can be severely limited by ametropia. Irregular astigmatisms are frequently encountered in these patients and is commonly associated with high degrees of hyperopia or myopia. This systematic review investigates the safety and efficacy of laser refractive surgery for post KP vision correction. 31 studies with 683 participants (732 eyes) enrolled in this review. Mean astigmatism improved significantly (mean difference [MD] = -2.70, 95% CI, -3.13 to -2.28, P < .0001). As well as Mean spherical equivalent (MD = -3.35, 95% CI, -3.92 to -2.78, P < .0001). From 586 participants 5.8% lost 2 or more lines of corrected distance visual acuity after treatment. The proportion of eyes with 20/40 uncorrected distance visual acuity or better was reported and the percentage was 46.79% overall. Laser refractive procedures (laser in situ keratomileusis [LASIK] or photorefractive keratectomy [PRK] or transepithelial PRK) on eyes with corneal transplantation were found to be relatively safe and effective. Our systematic review shows there is improvement in all outcomes. Main adverse effects were haze for PRK and epithelial ingrowth for LASIK.

Managing Post-Keratoplasty Astigmatism: High-Tech vs. Low-Tech Imaging Techniques for Guiding Suture Manipulation

Astigmatism is a visually significant condition that can develop after keratoplasty. The management of post-keratoplasty astigmatism can be performed both when transplant sutures are in place and when they have been removed. Fundamental for astigmatism management is its identification and characterization in terms of type, amount, and direction. Commonly, post-keratoplasty astigmatism is evaluated through corneal tomography or topo-aberrometry; however, many other techniques can be used in case these instruments are not readily available. Here, we describe several low-tech and high-tech techniques used for post-keratoplasty astigmatism detection in order to quickly understand if it contributes to low vision quality and to determine its characteristics. The management of post-keratoplasty astigmatism through suture manipulation is also described.

Management of post-keratoplasty ametropia

Even after a successful corneal transplant, patients experience severe refractive errors, impeding their rehabilitation and satisfaction. Refractive errors can be caused by recipient pathology and corneal thickness, as well as intraoperative factors such as donor-host discrepancy, recipient's eccentric trephination, vitreous length, wound apposition, technique of suturing, and suture material. Also, wound healing and the interim between keratoplasty and suture removal contribute to astigmatism. Lamellar keratoplasty outperforms penetrating keratoplasty in terms of endothelial cell loss and endothelial graft rejection, yet the risk of developing refractive errors is comparable. Nonsurgical interventions such as spectacles and lenses fail to provide desirable vision in cases with high astigmatism and corneal irregularity. When these limitations are encountered, surgical interventions including incisional keratotomy, wedge resection, laser refractive surgeries, intracorneal segments, and intraocular lens implantation are employed. However, occasionally, none of these approaches deliver the desired effects, leading to the need for a repeat keratoplasty.

Post Penetrating Keratoplasty Ectasia: Incidence, Risk Factors, Clinical Features, and Treatment Options

BACKGROUND: Corneal transplantation in keratoconus (KC) patients is generally considered to be successful with a high grade of patient satisfaction. Long-term studies suggest a 6% to 11% probability of KC recurrence manifested by keratometric instability and progressive corneal ectasia. METHODS: We propose to review the frequency, risk factors for the development, and the surgical options for the correction of high irregular astigmatism due to late graft ectasia following penetrating keratoplasty (PK). RESULTS: Post-keratoplasty ectasia is characterized by increasing corneal steepening with myopic shift and high irregular astigmatism, developing years or decades after PK, mostly occurring in KC patients. Contact lenses may adequately improve the visual acuity; however, because these patients are often elderly and intolerant to hard contact lenses, ultimately a surgical correction is proposed to the patient. Compressive suture and corneal wedge resection may improve corneal astigmatism, but the outcomes are unpredictable and often temporary. For this reason, a larger PK graft is often proposed for surgical rehabilitation with the consequence of removing more of the recipient’s healthy endothelium and exposing the patient to a renewed immunogenic stimulus and short-term graft failure for endothelial decompensation. More recently, lamellar keratoplasty using various techniques has been proposed as an alternative to PK in order to maximize the visual outcomes and minimize the complications. CONCLUSIONS: Management of advanced corneal ectasia is a significant challenge for corneal surgeons. Many surgical approaches have been developed, so there is a large arsenal of surgical operations to correct post-PK ectasia. Among them, large-diameter anterior lamellar keratoplasty may be a viable, safer, and effective alternative to PK for the correction of post-keratoplasty ectasia.

Graft Failure after PKP and DMEK: What is the Best Option?

Corneal transplantation is the most commonly performed human tissue transplantation procedure worldwide. Due to the large number of grafts, corneal graft failure has become one of the most common indications for corneal transplantation for immunological and non-immunological reasons (e.g. recurrence of underlying disease, high intraocular pressure, grafted guttae, transmitted HSV or CMV infection). The relatively recently developed lamellar grafting techniques have introduced certain potential complications that may lead to graft failure and require approaches other than penetrating keratoplasty for re-grafting. On the other hand, these new lamellar techniques also offer new possibilities for salvaging failed penetrating grafts, with potential advantages over successive penetrating keratoplasties, such as lower intraoperative risks, faster visual rehabilitation and reduced risk of immune reaction. Today, the patient with good healing who is satisfied with his graft before endothelial decompensation, with low astigmatism and no stromal scars, represents the optimal condition for DMEK after PKP. This can also be combined with phacoemulsification (so-called triple DMEK). Otherwise, a penetrating re-keratoplasty with a larger graft (typically excimer laser repeat PKP 8.5/8.6 mm) is performed to treat edema, scars and irregular astigmatism simultaneously. The medical history carries weight in this decision! Re-DMEK in case of graft failure after DMEK and DSAEK does not require any modification of the standard technique and leads to good visual acuity results if performed quickly. If there is clear stromal scarring after multiple (external) DMEKs, PKP can also be considered to rectify the situation. Otherwise causeless recurrent graft failures must suggest herpetic or CMV endotheliitis and, after PCR analysis of the aqueous humour aspirate, be treated appropriately with medication.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Corneal transplantation after failed grafts: Options and outcomes

Corneal transplantation is the most commonly performed human tissue transplantation procedure worldwide. Because of the large number of transplants, corneal graft failure has become one of the most common indications for corneal transplantation. The relatively recently developed lamellar transplant techniques have brought about specific potential complications leading to graft failure that may require different approaches to repeat transplantation other than penetrating keratoplasty. On the other hand, these new lamellar techniques also provide novel ways of rescuing failed penetrating grafts, with potential advantages over successive penetrating keratoplasties, such as reduced intraoperative risks and faster visual rehabilitation. We summarize the incidence and risk factors of graft failure for penetrating and lamellar (stromal and endothelial) corneal transplants and discuss the various surgical alternatives currently available to rescue such failed grafts, with a focus on the reported outcomes and limitations.

[Descemet membrane endothelial keratoplasty DMEK - Donor and recipient step by step]

In 2020 Descemet membrane endothelial keratoplasty (DMEK) has become the gold standard in Germany for the treatment of corneal endothelial diseases; however, the widespread use of DMEK was initially limited due to problems with donor preparation and the difficulty of correctly and gently unfolding the endothelial Descemet membrane (EDM) in the anterior chamber. Following the situational donor selection, the safe single-handed donor preparation of the cornea without tearing or even rupturing the EDM, including the indispensable peripheral semicircular orientation marking. Also presented is a step by step atraumatic loading of the glass cartridge, the introduction of the EDM roll into the anterior chamber, and its safe step by step unfolding based on (1) the sequential use of jets of fluid, (2) repeated tapping on the peripheral/central cornea, (3) controlled flattening of the anterior chamber, (4) use of air bubbles of defined size and finally, the fixation of the EDM in correct orientation to the back of the host cornea with a gas bubble. Since every wrong step with DMEK can have far-reaching consequences for patient and surgeon, this step by step pragmatic approach should minimize the incidence of donor tissue damage and failure in patient maneuvers.

Vector Analysis of Femtosecond Laser-Assisted Arcuate Keratotomy for Post-Keratoplasty Astigmatic Correction

PURPOSE

To study the astigmatic correction of high post-keratoplasty astigmatism using Femtosecond laser (FSL)-assisted Arcuate Keratotomy (FS-AK).

METHODS

A prospective interventional cohort study. We enrolled 17 eyes with high degree of irregular astigmatism, scheduled for FS-AK. FSL was used to perform paired arcuate incisions 1.00 mm inside the graft. Patients' uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and astigmatic change were recorded and followed up to 1 year after surgery. Vector analysis using Alpins' method was done to analyze the astigmatic correction.

RESULTS

FS-AK reduced the refractive astigmatism at final follow-up visit at 12 months (p = 0.0008, repeated-measures analysis of variance [ANOVA]). The procedure improved the UCVA over the follow-up period (p = 0.007, repeated-measures ANOVA), with a similar effect on the BCVA (p = 0.046, repeated-measures ANOVA). There was a mild correlation between the target-induced astigmatism and the surgically induced astigmatism (R2 = 0.245) with a tendency to overcorrect more than under correct the astigmatism. A constant rotational error in the counterclockwise direction was also detected.

CONCLUSIONS

FS-AK improves the visual outcome and reduces the refractive cylinder in post-penetrating keratoplasty astigmatism. The predictability of astigmatism correction was variable in reducing post-keratoplasty astigmatism. Refinement of the treatment nomogram for such cases is highly recommended.

Post-keratoplasty astigmatism management by relaxing incisions: a systematic review

Postoperative visual acuity can be limited by post-keratoplasty astigmatism, even with a clear corneal graft. Astigmatism management can be performed by selective suture removal, adjustment of sutures, optical correction, photorefractive procedures, wedge resection, intra-ocular lens implantation, intracorneal ring segments, relaxing incisions with or without compression sutures and repeated keratoplasty. Relaxing incisions can be made in the graft, graft-host interface or host cornea. Despite the unpredictability of the method because the flat and steep meridians are usually not orthogonal after penetrating keratoplasty, with asymmetric power distribution, all the studies showed an overall reduction of refractive, keratometric or topographic astigmatism, ranging from 30% to 72% with manual or femtosecond-assisted techniques. Most patients with astigmatism higher than 6 diopters had residual cylinder less than or equal to 3 diopters, which can be treated by laser excimer ablation or secondary intraocular lens implantation.

Penetrating Keratoplasty for Keratoconus - Excimer Versus Femtosecond Laser Trephination

BACKGROUND

In case of keratoconus, rigid gas-permeable contact lenses as the correction method of first choice allow for a good visual acuity for quite some time. In a severe stage of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no more tolerated. In case of existing contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis.

METHODS

In case of advanced keratoconus - especially after corneal hydrops due to rupture of Descemet's membrane - penetrating keratoplasty (PKP) still is the surgical method of first choice. Noncontact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and those with repeat grafts in case of "keratoconus recurrences" due to small grafts with thin host cornea. For donor trephination from the epithelial side, an artificial chamber is used. Wound closure is achieved with a double running cross-stitch suture according to Hoffmann. Graft size is adapted individually depending on corneal size ("as large as possible - as small as necessary"). Limbal centration will be preferred intraoperatively due to optical displacement of the pupil. During the last 10 years femtosecond laser trephination has been introduced from the USA as a potentially advantageous approach.

RESULTS

Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient centration, reduces "vertical tilt" and "horizontal torsion" of the graft in the recipient bed, thus resulting in significantly less "all-sutures-out" keratometric astigmatism (2.8 vs. 5.7 D), higher regularity of the topography (SRI 0.80 vs. 0.98) and better visual acuity (0.80 vs. 0.63) in contrast to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP. Refractive outcomes of femtosecond laser keratoplasty, however, resemble that of the motor trephine.

CONCLUSIONS

In contrast to the undisputed clinical advantages of excimer laser keratoplasty with orientation teeth/notches in keratoconus, the major disadvantage of femtosecond laser application is still the necessity of suction and applanation of the cone during trephination with intraoperative pitfalls and high postoperative astigmatism.

Small Incision Lenticule Extraction for Postkeratoplasty Myopia and Astigmatism

Purpose. To evaluate the visual and refractive outcomes after small incision lenticule extraction (SMILE) for treating myopia and myopic astigmatism after penetrating keratoplasty (PKP). Design. Case-series. Methods. Ten eyes of 10 patients with previous PKP and residual myopic astigmatism for whom pentacam imaging and thickness measurements were acceptable for laser vision correction. Manifest refraction (MR), uncorrected distance visual acuity (UDVA), and corrected distance visual acuity (CDVA) were obtained preoperatively and one day, one week, and one, 3, and 6 months postoperatively. Cases were operated on the VisuMax® femtosecond laser platform with 500 kHz repetition rate. Results. The mean correction ratio for spherical errors was 0.84 ± 0.19 D and for the mean refractive spherical equivalent (MRSE) was 0.79 ± 0.13 D. Vector analysis showed a mean astigmatism reduction at the intended axis of 67 ± 25.25%, a correction index of 0.81 ± 0.21, and an overall mean percentage of success of astigmatism surgery of 53 ± 37.9%. The postoperative MRSE was stable throughout the 6-month follow-up period. The efficacy index was 0.93 and the safety index was 1.12. Conclusion. SMILE for correction of post-PKP myopia and astigmatism is effective, safe, and stable with moderate accuracy and predictability. Centration of the treatment within the grafts was easily performed.

[Perspectives of laser-assisted keratoplasty: current overview and first preliminary results with the picosecond infrared laser (λ = 3 µm)]

BACKGROUND

This article provides a review of the current state of laser-assisted keratoplasty and describes a first proof of concept study to test the feasibility of a new mid-infrared (MIR) picosecond laser to perform applanation-free corneal trephination.

METHODS

The procedure is based on a specially adapted laser system (PIRL-HP2-1064 OPA-3000, Attodyne, Canada) which works with a wavelength of 3,000 ± 90 nm, a pulse duration of 300 ps and a repetition rate of 1 kHz. The picosecond infrared laser (PIRL) beam is delivered to the sample by a custom-made optics system with an implemented scanning mechanism. Corneal specimens were mounted on an artificial anterior chamber and subsequent trephination was performed with the PIRL under stable intraocular pressure conditions.

RESULTS

A defined corneal ablation pattern, e.g. circular, linear, rectangular or disc-shaped, can be selected and its specific dimensions are defined by the user. Circular and linear ablation patterns were employed for the incisions in this study. Linear and circular penetrating PIRL incisions were examined by macroscopic inspection, histology, confocal microscopy and environmental scanning electron microscopy (ESEM) for characterization of the incisional quality. Using PIRL reproducible and stable incisions could be made in human and porcine corneal samples with minimal damage to the surrounding tissue.

CONCLUSION

The PIRL laser radiation in the mid-infrared spectrum with a wavelength of 3 µm is exactly tuned to one of the dominant vibrational excitation bands of the water molecule, serves as an effective tool for applanation-free corneal incision and might broaden the armamentarium of corneal transplant surgery.

Repeat Descemet membrane endothelial keratoplasty after complicated primary Descemet membrane endothelial keratoplasty

PURPOSE

To describe the clinical outcome and complications of repeat Descemet membrane endothelial keratoplasty (re-DMEK).

DESIGN

Retrospective case series study at a tertiary referral center.

PARTICIPANTS

From a series of 550 consecutive DMEK surgeries with ≥ 6 months follow-up, 17 eyes underwent re-DMEK for graft detachment after initial DMEK (n = 14) and/or endothelial graft failure (n = 3). The outcomes were compared with an age-matched control group of uncomplicated primary DMEK surgeries.

METHODS

The re-DMEK eyes were evaluated for best-corrected visual acuity (BCVA), densitometry, endothelial cell density (ECD), pachymetry, and intraoperative and postoperative complications.

MAIN OUTCOME MEASURES

Feasibility and clinical outcome of re-DMEK.

RESULTS

In all eyes, re-DMEK was uneventful. At 12 months, 12 of 14 eyes (86%) achieved a BCVA of ≥ 20/40 (≥ 0.5); 8 of 14 eyes (57%) achieved ≥ 20/25 (≥ 0.8), 3 of 14 eyes (21%) achieved ≥ 20/20 (≥ 1.0), and 1 eye (7%) achieved 20/17 (1.2); 5 eyes were fitted with a contact lens. Average donor ECD decreased from 2580 ± 173 cells/mm(2) before to 1390 ± 466 cells/mm(2) at 6 months after surgery, and pachymetry from 703 ± 126 μm to 515 ± 39 μm, respectively. No difference in densitometry could be detected between re-DMEK and control eyes (P = 0.99). Complications after re-DMEK included primary graft failure (n = 1), secondary graft failure (n = 2), graft detachment requiring rebubbling (n = 1), secondary glaucoma (n = 2), cataract (n = 1), and corneal ulcer (n = 1). One eye received tertiary DMEK.

CONCLUSIONS

In the management of persistent graft detachment and graft failure after primary DMEK, re-DMEK proved a feasible procedure. Acceptable BCVA may be achieved, albeit lower than after DMEK in virgin eyes, and some cases may benefit from contact lens fitting. Complications after re-DMEK may be better anticipated than after primary DMEK because graft detachment and graft failure tended to recur, suggesting that intrinsic properties of the host eye play a role in graft adherence and graft failure.

[Astigmatism after keratoplasty: influence of orthotopic transplantation]

BACKGROUND

Patients undergoing corneal transplantation often suffer from postoperative reduced vision due to high astigmatism. This retrospective study analyzed the influence of heterotopic or orthotopic transplantation on astigmatism and visual outcome.

PATIENTS AND METHODS

In this study 373 eyes of 334 patients were analyzed. Group 1 (OT) contained 186 eyes, which underwent orthotopic transplantation (side of recipient and donor corresponded), whereas group 2 (HT) included 187 heterotopic keratoplasties (donor cornea placed in the recipient's contralateral side). After 1, 3, 6, 12 and 24 months the median of keratometric astigmatism, objective astigmatism, topographic astigmatism and best corrected visual acuity (BCVA) were assessed and compared between groups.

RESULTS

The long-term results showed no statistically significant differences regarding keratometric and objective astigmatism, whereas topographic astigmatism differed significantly (p = 0.04) after 3 months. We observed a lower astigmatism of 5.7 dpt (range 3.08-7.78 dpt) in group OT than in the group HT with 7.1 dpt (range 3.9-10.7 dpt). No differences were found at the other time points. The BCVA showed a significantly better effect after 1 month (p = 0.01) in the OT group of 0.2 (0.1-0.3) than in HT group of 0.1 (0.05/0.25). In the postoperative course no additional significant dissimilarities were documented.

CONCLUSIONS

Heterotopic and orthotopic keratoplasty show no significant long-term differences in astigmatism and visual outcom.

[DALK and penetrating laser keratoplasty for advanced keratoconus]

BACKGROUND

In cases of contact lens intolerance and/or central corneal scars, corneal transplantation is indicated for advanced keratoconus. This can be performed as deep anterior lamellar keratoplasty (DALK) or as penetrating keratoplasty (PKP). The German keratoplasty registry shows that the proportion of anterior lamellar grafts in Germany has remained stable at approximately 5 % in recent years.

METHODS

Up to now DALK has not been technically standardized but can result in a good visual acuity using the big bubble technique if Descemet's membrane is laid bare intraoperatively. In 10-20 % a conversion to PKP is required if perforation of Descemet's membrane occurs. In cases of advanced keratoconus PKP is still the method of first choice especially after corneal hydrops due to rupture of Descemet's membrane. Non-contact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and those with repeat grafts in cases of keratoconus recurrence due to the graft being too small. For donor trephination from the epithelial side, an artificial chamber is used. Wound closure is achieved by a double running cross-stitch suture according to Hoffmann. Graft size is adapted individually depending on corneal size (as large as possible and as small as necessary). Limbal centration is given priority intraoperatively due to optical displacement of the pupil.

RESULTS

Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient centration, reduces vertical tilt and horizontal torsion of the graft in the recipient bed, thus resulting in significantly less all-sutures-out keratometric astigmatism (2.8 D versus 5.7 D), higher regularity of the topography (SRI 0.80 vs. 0.98) and better visual acuity (0.80 vs. 0.63) in contrast to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP.

CONCLUSIONS

In cases with optimal course DALK achieves the same visual outcome as mechanical PKP but the healthy endothelium can be preserved and endothelial immune reactions are prevented in keratoconus. In contrast to the undisputed clinical advantages of excimer laser keratoplasty with orientation teeth/notches in keratoconus, the major disadvantage of femtosecond laser application is still the necessity of suction and applanation of the cone during trephination.

Femtosecond laser technology in corneal refractive surgery: a review

PURPOSE

To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures.

METHODS

Literature review.

RESULTS

From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use.

CONCLUSIONS

Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility.

[Perspectives of excimer laser-assisted keratoplasty]

BACKGROUND AND PURPOSE

The purpose of this paper is to demonstrate the evolution of laser keratoplasty and to outline the potential future perspectives of this technique.

METHODS

For non-contact donor trephination from the epithelial side an artificial anterior chamber has been used. Since 1989 more than 3,300 penetrating keratoplasty operations (PKP) have been performed successfully with the Zeiss-Meditec MEL60® excimer laser in Erlangen and Homburg/Saar.

RESULTS

Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient decentration, reduces vertical tilt and horizontal torsion of the graft in the recipient bed, thus resulting in significantly less all-sutures-out keratometric astigmatism, higher regularity of the topography and better visual acuity. Besides less blood-aqueous barrier breakdown during the early postoperative course after PKP, excimer laser trephination does not induce cataract formation and does not impair the graft endothelium. Likewise, the rate of immunological graft rejections is not adversely affected by the excimer laser. In addition, trephination of an instable cornea is facilitated.

CONCLUSIONS

Because of undisputed clinical advantages, especially in eyes with keratoconus, excimer laser trephination with orientation teeth/notches is still favored in Homburg/Saar in daily practice. The femtosecond laser (FSL)-assisted keratoplasty technique is very exciting but a prospective randomized study is required to determine potential benefits over excimer laser PKP.

Current approaches for management of postpenetrating keratoplasty astigmatism

A successful corneal graft requires both clarity and an acceptable refraction. A clear corneal graft may be an optical failure if high astigmatism limits visual acuity. Intraoperative measures to reduce postkeratoplasty astigmatism include round and central trephination of cornea with an adequate size, appropriate sutures with evenly distributed tension, and perfect graft-host apposition. Suture manipulation has been described for minimising early postoperative astigmatism. If significant astigmatism remains after suture removal, which cannot be corrected by optical means, then further surgical procedures containing relaxing incisions, compression sutures, laser refractive surgery, insertion of intrastromal corneal ring segments, wedge resection, and toric intraocular lens implantation can be performed. When astigmatism cannot be reduced using one or more abovementioned approaches, repeat penetrating keratoplasty should inevitably be considered. However, none of these techniques has emerged as an ideal one, and corneal surgeons may require combining two or more approaches to exploit the maximum advantages.

Femtosecond laser arcuate keratotomy for the correction of high astigmatism after keratoplasty

PURPOSE

To determine the feasibility and initial outcomes of using a femtosecond laser to perform arcuate keratotomies to correct high post-keratoplasty astigmatism.

DESIGN

Prospective noncomparative interventional case series.

PARTICIPANTS

Twelve eyes of 12 consecutive patients (mean age 44.9+/-9.5 years) who presented with a high degree of astigmatism, noncorrectable with spectacles or contact lenses (10 post-penetrating keratoplasty, 2 post-deep lamellar keratoplasty), and were candidates for relaxing incisional corneal surgery.

METHODS

The Femtec (20/10 Perfect Vision, GmbH, Heidelberg, Germany) femtosecond laser performed paired 90-degree angled arcuate incisions on the graft button. The incision sites and depths were programmed at 1.00 mm inside the graft edge and at 90% of the corresponding local graft thickness, whereas the angular lengths of the cuts were determined by analyzing the locations and extents of the steepest meridians in the topographic map.

MAIN OUTCOME MEASURES

Changes in uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), mean subjective and topographically determined astigmatism; imaging of incisions by anterior segment optical coherence tomography (AS-OCT); and wound healing by in vivo confocal microscopy (IVCM).

RESULTS

Postoperative follow-up extended to 6 months. Mean uncorrected logarithm of the minimum angle of resolution (logMAR) BSCVA and UCVA improved from preoperative values of 0.25+/-0.16 and 1.05+/-0.18 to 6-month values of 0.11+/-0.12 (standard deviation) and 0.55+/-0.34, respectively (P<0.05). Mean subjective astigmatism was 7.16+/-3.07 diopters (D) preoperatively and 2.23+/-1.55 D at 1 month after surgery (P = 0.002) and remained stable to the end of follow-up. Anterior segment optical coherence tomography image analysis showed that the depth and location of the incisions were consistent with the preoperative surgical plan. In vivo confocal microscopy showed mild edema and keratocyte activation along the incision edges, together with initial epithelial ingrowth inside the wound, followed by subsequent moderate fibrotic scarring.

CONCLUSIONS

Arcuate keratotomies performed with the femtosecond laser were effective in reducing post-keratoplasty astigmatism. Laser-generated incisions within the graft button presented precise geometry and reliable depth of incision, with a wound healing pattern characterized by epithelial ingrowth and mild fibrosis.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Anterior lamellar keratoplasty over penetrating keratoplasty for optical, therapeutic, and tectonic indications: a case series

PURPOSE

To report a consecutive case series of patients who underwent anterior lamellar keratoplasty (ALK) over a preexisting penetrating keratoplasty (PK).

DESIGN

Retrospective, interventional case series.

METHODS

Eight patients (8 eyes) were identified from the Singapore Corneal Transplant Study database, in a single institution (Singapore National Eye Center) from patients who underwent ALK performed over a PK. Main outcome measures were final visual acuity (VA), graft failure (ALK, PK or both), successful restoration of tectonic integrity in tectonic indications, and eradication of infection in therapeutic cases.

RESULTS

The indications for surgery were therapeutic in 3 patients, optical in 3 patients, and tectonic in 2 patients. Postoperatively the best-corrected visual acuity (BCVA) improved in 5 eyes and remained unchanged in 3 eyes. Mean VA improved significantly after ALK; the mean preoperative BCVA was 1.52 +/- 0.25 and the mean postoperative BCVA was 0.87 +/- 0.26 (P = .032). Three of the 8 eyes post-lamellar keratoplasty (LK) managed to attain a BCVA equal to post-PK BCVA. Two patients had suture micro-perforations while 1 patient required a repeat ALK for recurrence of infection.

CONCLUSION

ALK may be a considered as a viable alternative to a repeat PK for a variety of optical, therapeutic, and tectonic indications.

Femtosecond-laser arcuate wedge-shaped resection to correct high residual astigmatism after penetrating keratoplasty

We describe a standardized technique of femtosecond (FS) laser arcuate resection (LAR) in which intersecting arcuate cuts are used to perform a wedge resection for the correction of high astigmatism. A simple formula was used to calculate the relative decentration of the arcuate cuts based on the radii of curvature and desired wedge width to be resected. Feasibility of the procedure was established in porcine corneas before treatment of a patient with 20 diopters (D) of post-keratoplasty astigmatism. The astigmatism was reversed. Suture removal resulted in reduction of 14.5 D of astigmatism. Laser arcuate resection can be an effective alternative to manual wedge resection, allowing easier, more controlled, and more precise excision of tissue in width, length, and depth.

[The penetrating keratoplasty. A 100-year success story]

Ten precautions for prophylaxis of astigmatism in penetrating keratoplasty are recommended:1. The attempt should be made to determine donor topography for exclusion of previous refractive surgery, keratoconus/high astigmatism, and to allow for "harmonization" of donor and recipient topography.2. Donor and recipient trephination should be performed from the epithelial side with the same system, which is the prerequisite for congruent cut surfaces and angles in donor and recipient. For this purpose an artificial anterior chamber is used for donor trephination.3. Orientation structures in donor and host facilitate the correct placement of the first four or eight cardinal sutures to avoid horizontal torsion.4.A measurable improvement seems to be possible, using the Krumeich guided trephine system (GTS), the second generation Hanna trephine, and the Erlangen technique of nonmechanical trephination with the excimer laser.5. Horizontal positioning of the head and limbal plane are indispensable for state-of-the-art PKP surgery in order to avoid decentration, vertical tilt, and horizontal torsion.6. Graft size should be adjusted individually ("as large as possible, as small as necessary").7. Limbal centration should be preferred over pupil centration (especially in keratoconus).8. Excessive graft over- or undersize should be avoided to prevent stretching or compression of peripheral donor tissue.9. As long as Bowman's layer is intact a double running cross-stitch suture (according to Hoffmann) is preferred since it results in higher topographic regularity, earlier visual rehabilitation, and less suture loosening requiring only rarely suture replacement.10.Intraoperative keratoscopy should be applied after removal of lid specula and fixation sutures.